Sensitivity study on the counter-current flow limitation in the DEG LBLOCA with the TRACE code

Abstract

The counter-current flow limitation (CCFL) model plays a key role in any large break loss of coolant accident (LBLOCA) analysis since it affects the calculated discharge flow, reflooding time and peak cladding temperature (PCT). In this paper, a sensitivity study on the CCFL model is performed, by modeling LBLOCA occurring at the Chinshan BWR/4 plant. The scenario assumes 102% power and 75% core flow, with a double-ended guillotine (DEG) break on the recirculation loop, which is the most limiting LBLOCA for a BWR/4 reactor. Two break locations, i.e. on the suction and the discharge side of a recirculation pump, are evaluated, with high pressure core injecting (HPCI) and low pressure core spraying (LPCS) available while low pressure core injecting (LPCI) has failed. The TRACE code is used for the analysis. The Chinshan TRACE model was benchmarked against steady-state and transient data contained in the plant FSAR report, as well as start-up data and the transient results using the RETRAN code. The thermal hydraulic phenomena in the lower plenum area and the jet pumps are also analyzed.